linux-kernel - Re: [PATCH] rtc: 88pm860x: prevent use-after-free on device remove

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Message-ID: <20190426185717.GV14604@piout.net>
Date:   Fri, 26 Apr 2019 20:57:17 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Sven Van Asbroeck <thesven73@...il.com>
Cc:     Alessandro Zummo <a.zummo@...ertech.it>, linux-rtc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rtc: 88pm860x: prevent use-after-free on device remove

On 26/04/2019 14:36:35-0400, Sven Van Asbroeck wrote:
> The device's remove() attempts to shut down the delayed_work scheduled
> on the kernel-global workqueue by calling flush_scheduled_work().
> 
> Unfortunately, flush_scheduled_work() does not prevent the delayed_work
> from re-scheduling itself. The delayed_work might run after the device
> has been removed, and touch the already de-allocated info structure.
> This is a potential use-after-free.
> 
> Fix by calling cancel_delayed_work_sync() during remove(): this ensures
> that the delayed work is properly cancelled, is no longer running, and
> is not able to re-schedule itself.
> 
> This issue was detected with the help of Coccinelle.
> 
> Signed-off-by: Sven Van Asbroeck <TheSven73@...il.com>
> ---
>  drivers/rtc/rtc-88pm860x.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
Applied, thanks.

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com